Ceramic-metal bonded body

ABSTRACT

To form an electrostatic chuck, a bonding sheet is applied onto the upper surface of a cooling plate and then the cooling plate is placed in a vacuum dryer at a pressure of 2,000 Pa or less for a pre-bake treatment at 120° C. to 130° C. for 15 to 40 hours, followed by natural cooling. A plate is then stacked on the bonding sheet so that the lower surface of the plate is aligned with the upper surface of the bonding sheet, which is applied onto the cooling plate. The resulting stacked body is placed in a heat-resistant resin bag, and is then placed in an autoclave and treated together for several hours under pressure and heat.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 13/213,542,filed Aug. 19, 2011, which in turn is a continuation of InternationalApplication No. PCT/JP2010/052557, filed Feb. 19, 2010, and claims thebenefit under 35 USC §119(e) of U.S. Provisional Application No.61/154,000, filed Feb. 20, 2009, the entireties of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a ceramic-metal bonded body and amethod of producing the same.

BACKGROUND OF THE INVENTION

An electrostatic chuck is a component used in an etching step which isone step of semiconductor manufacturing processing. More specifically,an electrostatic chuck is a component used for performing a uniformetching process on a silicon wafer by applying suction to the siliconwafer through a Johnsen-Rahbek force or a Coulomb force in a vacuum anduniformly cooling heat generated in etching. Examples of functionsnecessary for this component include (1) a vacuum holding power, (2) aresponsiveness of applying suction to and releasing a silicon wafer, (3)a property for making the temperature of the entire surface of thesilicon wafer subjected to suction uniform, and (4) corrosion resistanceagainst chemicals used in etching. A known example of such anelectrostatic chuck is an electrostatic chuck in which a ceramic plateis bonded to a supporting base composed of a metal such as aluminum witha bonding material composed of a silicone resin therebetween (forexample, JP 04-287344 A1).

SUMMARY OF THE INVENTION

However, when the existing electrostatic chuck is used at a hightemperature of 80° C. or higher, gas is generated from the bondingmaterial, and thus bubbles are formed between the plate and the bondingmaterial and between the supporting base and the bonding material. Thesebubbles may decrease the contact area between the plate and thesupporting base and cause variations in the bonding performance, therebydecreasing the temperature uniformity of a wafer subjected to suction.Furthermore, in the case where a heater is buried in the plate so as tocontrol the temperature of the wafer to be constant, the temperaturecontrol may become difficult because the amount of heat transfer ischanged by the generation of such bubbles. These problems also occur incomponents having structures similar to the electrostatic chuck, thatis, ceramic-metal bonded bodies. An example of the components havingstructures similar to the electrostatic chuck is a showerhead. Theshowerhead is a component used for supplying and dispersing a reactantgas to a chamber of a plasma processing apparatus used in a step ofsemiconductor manufacturing processing.

The present invention has been made in order to solve the aboveproblems, and a main object of the present invention is to prevent adecrease in the contact area and variations in the bonding performancebetween a plate and a supporting base of a ceramic-metal bonded body.

The present invention is directed to a method of producing aceramic-metal bonded body by bonding a ceramic plate to a metalsupporting base with a bonding sheet containing a resin as a maincomponent, the method including a pre-bake step of heating the bondingsheet in air, in an inert gas, or in a vacuum in advance to reduce theamount of volatile components in the bonding sheet; and a bonding stepof bonding the plate to the supporting base with the bonding sheettherebetween by placing the plate, the supporting base, and the bondingsheet in an airtight bag, reducing pressure in the airtight bag, andperforming heating at a temperature lower than that of the pre-bake stepwhile applying a pressure in an autoclave.

In this production method, the bonding sheet is heated in advance toreduce the amount of volatile components in the bonding sheet, and theplate is then bonded to the supporting base with the bonding sheettherebetween by placing the plate, the supporting base, and the bondingsheet in a pressure-reduced airtight bag and by applying a pressure tothe resulting stacked body in an autoclave. Accordingly, even when theresulting ceramic-metal bonded body is used at high temperatures, gas isnot generated from the bonding sheet, and thus no bubbles are generatedbetween the plate and the bonding material and between the supportingbase and the bonding material. As a result, a decrease in the contactarea between the plate and the supporting base does not occur, andvariations in the bonding performance are not generated.

Herein, examples of the plate include plates composed of a ceramic suchas silicon carbide, aluminum nitride, alumina, calcium titanate, orbarium titanate. Examples of the supporting base include supportingbases composed of aluminum or silicon, and supporting bases composed ofa metal-based composite material obtained by impregnating a porousceramic base material with a metal. Examples of the bonding sheetinclude bonding sheets composed of an acrylic resin or a silicone resin.The heating conditions in the pre-bake step are appropriately determinedin accordance with the material of the bonding sheet. Specifically, theeffects of the atmosphere gas, the degree of vacuum, the heatingtemperature, and the heating time on the bonded interface between theplate and the supporting base are examined by experiments in advance foreach material of the bonding sheet. Numerical ranges are then determinedin which the bonded interface is not affected and bubbles are notgenerated from the bonding sheet even when the bonding sheet is heatedto a high temperature. The atmosphere in the pre-bake step is preferablyan inert gas, and more preferably vacuum rather than air because it ispossible to obtain a ceramic-metal bonded body in which separation doesnot occur and bubbles are not generated at the bonded interface evenwhen the ceramic-metal bonded body is used at higher temperatures. Thebonding sheet preferably has a thickness of 0.1 to 0.3 mm and preferablycontains metal filler (e.g., aluminum filler). In the bonding step, asufficient bonding strength can be obtained by conducting a treatmentunder pressure and heat in the autoclave.

In the method of producing a ceramic-metal bonded body according to thepresent invention, in the pre-bake step, the bonding sheet may beapplied onto the supporting base, and the supporting base to which thebonding sheet is applied may be heated to reduce the amount of volatilecomponents in the bonding sheet. Alternatively, the bonding sheet may beapplied onto the plate, and the plate to which the bonding sheet isapplied may be heated to reduce the amount of volatile components in thebonding sheet. In this case, the production method of the presentinvention can be performed without using a new jig.

In the method of producing a ceramic-metal bonded body according to thepresent invention, in the pre-bake step, a frame which is a board havingan opening having the same shape as the bonding sheet of theceramic-metal bonded body and a large-size sheet which is formed intothe bonding sheet may be prepared, the large-size sheet may be appliedonto the frame so that the large-size sheet covers the opening of theframe, and the frame to which the large-size sheet is applied may beheated to reduce the amount of volatile components in the large-sizesheet. In this case, the heating time in the pre-bake step can beshortened as compared with the case where the amount of volatilecomponents is reduced by performing heating after the bonding sheet isapplied onto the supporting base and the case where the amount ofvolatile components is reduced by performing heating after the bondingsheet is applied onto the plate. This is because the volatile componentsare volatilized from one surface of the sheet in the former two methodsdescribed above, whereas the volatile components are volatilized fromboth surfaces of the sheet in the latter method using the frame.

In the method of producing a ceramic-metal bonded body according to thepresent invention, the resin may be an acrylic resin, and heatingconditions in the pre-bake step may be 15 to 30 hours at 120° C. to 130°C. in air. The pre-bake step is preferably performed at 1 atm in anatmosphere of an inert gas such as nitrogen or argon instead of air.Furthermore, the pre-bake step may be performed in a vacuum atmosphereof 2,000 Pa or less (preferably 10 Pa or less, and more preferably 1 Paor less) at 120° C. to 130° C. for 15 to 30 hours. As for bondingconditions in the bonding step, the body to be bonded may be placed in aheat-resistant resin bag, the resin bag may be degassed and then sealed,and the body to be bonded and the bag containing the body may besubjected to bonding together by a treatment under pressure and heat inan autoclave. The bonding under pressure and heat is preferablyperformed under the conditions of a temperature lower than thetemperature of the pre-bake step, e.g., at 100° C., and a pressure of 10to 20 MPa. Under these conditions, in the case where a bonding sheetcomposed of an acrylic resin is used, it is possible to obtain aceramic-metal bonded body in which separation does not occur and bubblesare not generated at the bonded interface. Herein, a heating temperatureof lower than 120° C. in the pre-bake step is not preferable becausebubbles are generated at the bonded interface when the resulting bondedbody is used at high temperatures. A heating temperature of higher than130° C. is not preferable because the quality of the bonding sheet isdegraded, thereby decreasing the bonding performance. A heating time ofshorter than 15 hours in the pre-bake step is not preferable becausebubbles may be generated at the bonded interface when the resultingbonded body is used at high temperatures. A heating time of longer than30 hours is not preferable because the heating time is unnecessarilylong and the productivity decreases, though there is no problem in termsof quality of the resulting bonded body.

In the method of producing a ceramic-metal bonded body according to thepresent invention, the resin may be a silicone resin, and heatingconditions in the pre-bake step may be 15 to 30 hours at 140° C. to 170°C. in air. The pre-bake step is preferably performed at 1 atm in anatmosphere of an inert gas such as nitrogen or argon instead of air.Furthermore, the pre-bake step may be performed in a vacuum atmosphereof 2,000 Pa or less (preferably 10 Pa or less, and more preferably 1 Paor less) at 140° C. to 170° C. for 15 to 30 hours. As for bondingconditions in the bonding step, the body to be bonded may be placed in aheat-resistant resin bag, the resin bag may be degassed and then sealed,and the body to be bonded and the bag containing the body may besubjected to bonding together by a treatment under pressure and heat inan autoclave. The bonding under pressure and heat is preferablyperformed under the conditions of a temperature 10° C. to 30° C. lowerthan the temperature of the pre-bake step, e.g., in the range of 120° C.to 140° C., and a pressure of 10 to 20 MPa. Under these conditions, inthe case where a bonding sheet composed of a silicone resin is used, itis possible to obtain a ceramic-metal bonded body in which separationdoes not occur and bubbles are not generated at the bonded interface.Herein, a heating temperature of lower than 140° C. in the pre-bake stepis not preferable because bubbles are generated at the bonded interfacewhen the resulting bonded body is used at high temperatures. A heatingtemperature of higher than 170° C. is not preferable because the qualityof the bonding sheet is degraded, thereby decreasing the bondingperformance. A heating time of shorter than 15 hours in the pre-bakestep is not preferable because bubbles may be generated at the bondedinterface when the resulting bonded body is used at high temperatures. Aheating time of longer than 30 hours is not preferable because theheating time is unnecessarily long and the productivity decreases,though there is no problem in terms of quality of the resulting bondedbody.

In the method of producing a ceramic-metal bonded body according to thepresent invention, the ceramic-metal bonded body may be an electrostaticchuck used for fixing a wafer by applying suction in a semiconductormanufacturing process or a showerhead used for supplying a reactant gasto a chamber in a semiconductor manufacturing process.

The present invention is also directed to a bonded body including aceramic plate, a metal supporting base, and a resin bonding sheet thatbonds the plate to the supporting base, wherein when the bonded body isheated in a vacuum environment of 100 Pa at 120° C. for 300 hours, theamount of change in the weight of the bonding sheet is 50 μg/cm² (wherethe unit is microgram per square centimeter of a bonded surface) orless. Alternatively, in this case, no bubbles are generated at a bondedinterface between the plate and the bonding sheet and a bonded interfacebetween the supporting base and the bonding sheet.

This ceramic-metal bonded body can be obtained by the method ofproducing a ceramic-metal bonded body according to the presentinvention. Since the amount of volatile components in the bonding sheetis reduced in the production, the amount of change in the weight of thebonding sheet is very small even when the ceramic-metal bonded body isexposed to high temperatures.

The ceramic-metal bonded body according to the present invention may bean electrostatic chuck used for fixing a wafer by applying suction in asemiconductor manufacturing process or a showerhead used for supplying areactant gas to a chamber in a semiconductor manufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a schematic configuration of aplasma processing apparatus 10 including an electrostatic chuck 20.

FIG. 2 includes explanatory views showing a first method of producing anelectrostatic chuck 20.

FIG. 3 includes explanatory views showing a second method of producingan electrostatic chuck 20.

FIG. 4 includes explanatory views showing the first half of a thirdmethod of producing an electrostatic chuck 20.

FIG. 5 includes explanatory views showing the second half of the thirdmethod of producing an electrostatic chuck 20.

FIG. 6 is a graph showing an example of a temperature history of apre-bake treatment.

FIG. 7 is a graph showing an example of a temperature history of apre-bake treatment.

FIG. 8 includes charts showing analytical results of gaschromatography-mass spectrometry (GC-MS) of gas components.

FIG. 9 is a graph showing a relationship between the elapsed time fromthe start of control and the amount of shift of the electric power.

FIG. 10 is a graph showing a relationship between the elapsed time fromthe start of control and the amount of shift of the electric power.

DETAILED DESCRIPTION OF THE INVENTION

Next, embodiments for carrying out the present invention will bedescribed with reference to the drawings. FIG. 1 is a cross-sectionalview showing a schematic configuration of a plasma processing apparatus10 including an electrostatic chuck 20 and a showerhead 60.

As shown in FIG. 1, the plasma processing apparatus 10 includes a metal(e.g., an aluminum alloy) chamber 12, the internal pressure of which canbe controlled, and an electrostatic chuck 20 and a showerhead 60 thatare arranged in the chamber 12.

The chamber 12 is configured so that a reactant gas can be supplied froma gas supply path 14 to the showerhead 60 and the internal pressure ofthe chamber 12 can be reduced to a predetermined degree of vacuum usinga vacuum pump connected to an evacuation path 16.

The electrostatic chuck 20 includes a plate 22 that can apply suction toa silicon wafer W to be subjected to a plasma treatment, a cooling plate28 disposed on the reverse face of the plate 22 and functioning as asupporting base, and a bonding sheet 32 that bonds the plate 22 to thecooling plate 28.

The plate 22 is a disc-shaped ceramic component having a step-likeportion on the outer circumference thereof, and the outer diameter of awafer placing surface 23 is smaller than the outer diameter of the waferW. This plate 22 includes an electrostatic electrode 24 and a resistanceheating element 26 therein. The electrostatic electrode 24 is a planarelectrode to which a direct-current voltage can be applied by anexternal power supply (not shown). Upon applying a direct-currentvoltage to this electrostatic electrode 24, the wafer W is fixed to thewafer placing surface 23 by applying suction through a Coulomb force ora Johnsen-Rahbek force. Upon releasing the application of thedirect-current voltage, the fixation of the wafer W to the wafer placingsurface 23 by the suction is released. The resistance heating element 26is formed as a pattern, for example, in the shape of a single brushstroke so that the resistance heating element 26 is arranged over theentire surface of the plate 22. When a voltage is applied, theresistance heating element 26 generates heat to heat the wafer W. Thevoltage can be applied to the resistance heating element 26 withbar-shaped terminals (not shown) extending from the reverse face of thecooling plate 28 to each end of the resistance heating element 26. Inthe case where the plate 22 is formed of alumina, the plate 22 functionsas a Coulomb-type electrostatic chuck because of a high volumeresistivity of alumina. In the case where the plate 22 is formed ofaluminum nitride, the plate 22 functions as a Johnsen-Rahbek-typeelectrostatic chuck because the volume resistivity of aluminum nitrideis lower than that of alumina.

The cooling plate 28 is a disc-shaped aluminum component having astep-like portion on the outer circumference thereof. The outer diameterof the upper surface of the cooling plate 28, the upper surface facingthe plate 22, is the same as the outer diameter of the lower surface ofthe plate 22. The cooling plate 28 includes a cooling medium path 30through which a cooling medium (for example, water) cooled by anexternal cooling unit (not shown) circulates. This cooling medium path30 is formed, for example, in the shape of a single brush stroke so thatthe cooling medium passes through the entire surface of the coolingplate 28. The cooling plate 28 is fixed to a bottom surface of thechamber 12 with bolts (not shown). Thus, the whole electrostatic chuck20 is fixed in the chamber 12. A protective ring (not shown) may bearranged on the step-like portion provided on the outer circumference ofthe cooling plate 28. The protective ring is formed so as not to contactthe wafer W and protects the cooling plate 28 from a plasma during theplasma treatment of the wafer W. The protective ring can be replacedaccording to need. Examples of the material of the protective ringinclude quartz, alumina, and metal silicon.

The bonding sheet 32 is a layer bonding the plate 22 to the coolingplate 28. The outer diameter of the bonding sheet 32 is the same as theouter diameter of the lower surface of the plate 22 and the outerdiameter of the upper surface of the cooling plate 28. This bondingsheet 32 is subjected to a pre-bake treatment described below, is thenplaced in an airtight bag in a state in which the bonding sheet 32 issandwiched between the plate 22 and the cooling plate 28, and isvacuum-packed by reducing the pressure in the bag. The whole airtightbag is placed in an autoclave and is treated under pressure and heat.The bonding sheet 32 is preferably composed of an acrylic resin or asilicone resin. The thickness of the bonding sheet 32 is preferably 100to 300 μm.

The showerhead 60 includes a disc-shaped ceramic plate 62 used forsupplying and dispersing a reactant gas to the chamber 12, a truncatedcone-shaped metal electrode plate 64 functioning as an upper electrodefor generating a plasma, and a bonding sheet 66 bonding the plate 62 tothe metal electrode plate 64. A plurality of small holes 60 apenetrating through the plate 62, the bonding sheet 66, and the metalelectrode plate 64 in the vertical direction are provided in theshowerhead 60. The metal electrode plate 64 includes a sheath heater 65therein. This sheath heater 65 is formed over the entire surface of themetal electrode plate 64 in the shape of a single brush stroke. Thisbonding sheet 66 is subjected to a pre-bake treatment described below,is then vacuum-packed in a state in which the bonding sheet 66 issandwiched between the plate 62 and the metal electrode plate 64, isplaced in an autoclave, and treated under pressure and heat. The bondingsheet 66 is preferably composed of an acrylic resin or a silicone resin.The showerhead 60 is arranged and fixed so that the upper surface of themetal electrode plate 64 contacts a cooling plate 68 attached to thechamber 12. The cooling plate 68 includes a cooling medium path 72through which a cooling medium (for example, water) cooled by anexternal cooling unit (not shown) circulates. The cooling plate 68 isconfigured so that a reactant gas, which is supplied from the gas supplypath 14 connected to the chamber 12 through a gas-holding portion 76, issupplied to the small holes 60 a of the showerhead 60 throughdistribution paths 74.

Next, an example of the use of the plasma processing apparatus 10 havingthe above configuration will be described. First, a cooling mediumcooled to a predetermined temperature (for example, 25° C.) with anexternal cooling unit (not shown) is circulated through the coolingmedium paths 30 and 72. Subsequently, the wafer W is placed on the waferplacing surface 23 of the plate 22. The pressure in the chamber 12 isreduced by a vacuum pump so that the degree of vacuum in the chamber 12is adjusted to a predetermined value. A direct-current voltage isapplied to the electrostatic electrode 24 to generate a Coulomb force ora Johnsen-Rahbek force so that the wafer W is fixed to the wafer placingsurface 23 by applying suction. Next, the atmosphere in the chamber 12is controlled to be a reactant gas atmosphere at a predeterminedpressure (for example, several tens of Pa to several hundred Pa). Inthis state, a high-frequency voltage is applied between the metalelectrode plate 64 of the showerhead 60 and the electrostatic electrode24 of the electrostatic chuck 20 in the chamber 12 to generate a plasma.In this embodiment, both the direct-current voltage for generating anelectrostatic force and the high-frequency voltage are applied to theelectrostatic electrode 24. Alternatively, the high-frequency voltagemay be applied to the cooling plate 28 instead of the electrostaticelectrode 24. The surface of the wafer W is etched by the generatedplasma. In this step, the temperature of the wafer W is controlled to beconstant by adjusting the electrical energy supplied to the resistanceheating element 26 or by adjusting the flow rate of the cooling mediumcirculating through the cooling medium path 30 of the cooling plate 28.Furthermore, the temperature of the showerhead 60 is controlled to beconstant by adjusting the electrical energy supplied to the sheathheater 65 or by adjusting the flow rate of the cooling mediumcirculating through the cooling medium path 72 of the cooling plate 68.

Next, methods of producing an electrostatic chuck 20 will be described.FIG. 2 includes explanatory views showing a first method of producing anelectrostatic chuck 20. FIG. 3 includes explanatory views showing asecond method of producing an electrostatic chuck 20. FIGS. 4 and 5include explanatory views showing a third method of producing anelectrostatic chuck 20.

First, the first production method will be described with reference tothe explanatory views of FIG. 2. First, a plate 22, a cooling plate 28,and a double-sided adhesive bonding sheet 32 composed of a resin areprepared (refer to FIG. 2( a)). A bonding sheet having the same shape asthe lower surface of the plate 22 and the upper surface of the coolingplate 28 is prepared as the bonding sheet 32. Next, the bonding sheet 32is applied onto the upper surface of the cooling plate 28 (refer to FIG.2( b)). Subsequently, the cooling plate 28 to which the bonding sheet 32is applied is placed in a dryer, and a pre-bake treatment is conductedin an air atmosphere, or in an atmosphere in which air in the dryer isreplaced with an inert gas such as nitrogen or argon, or in anatmosphere in which the pressure in the dryer is reduced to 2,000 Pa orless (preferably 10 Pa or less, and more preferably 1 Pa or less) (referto FIG. 2( c)). In the case where the bonding sheet 32 is composed of anacrylic resin, the pre-bake treatment is conducted at 120° C. to 130° C.for 15 to 30 hours, and natural cooling is then conducted in the dryer.FIG. 6 shows an example of a temperature history of this case. On theother hand, in the case where the bonding sheet 32 is composed of asilicone resin, the pre-bake treatment is conducted at 140° C. to 170°C. for 15 to 30 hours, and natural cooling is then conducted in thedryer in a vacuum. FIG. 7 shows an example of a temperature history ofthis case. The amount of volatile components in the bonding sheet 32 isreduced by this pre-bake treatment. After the pre-bake treatment, theplate 22 is stacked on the bonding sheet 32 so that the lower surface ofthe plate 22 is aligned with the upper surface of the bonding sheet 32applied onto the cooling plate 28 (refer to FIG. 2( d)). The resultingstacked body is placed in a heat-resistant resin bag, and is then placedin an autoclave. The stacked body in the heat-resistant resin bag istreated for 3 to 6 hours at a pressure of 10 to 20 MPa under heating ata temperature 10° C. to 30° C. lower than the temperature of thepre-bake treatment. Thus, the plate 22 is closely bonded to the coolingplate 28, with the bonding sheet 32 therebetween, to obtain anelectrostatic chuck 20 (refer to FIG. 2( e)).

Next, the second production method will be described with reference tothe explanatory views of FIG. 3. First, a plate 22, a cooling plate 28,and a double-sided adhesive bonding sheet 32 composed of a resin areprepared (refer to FIG. 3( a)). A bonding sheet similar to that used inthe first production method is prepared as the bonding sheet 32. Next,the bonding sheet 32 is applied onto the lower surface of the plate 22(refer to FIG. 3( b)). Next, the plate 22 to which the bonding sheet 32is applied is placed in a dryer, and a pre-bake treatment is conductedin an air atmosphere, or in an atmosphere in which air in the dryer isreplaced with an inert gas such as nitrogen or argon, or in anatmosphere in which the pressure in the dryer is reduced to 2,000 Pa orless (preferably 10 Pa or less, and more preferably 1 Pa or less) (referto FIG. 3( c)). The pre-bake treatment is conducted under the sameconditions as the first production method. Thus, the amount of volatilecomponents in the bonding sheet 32 is reduced. After the pre-baketreatment, the plate 22 is stacked on the cooling plate 28 so that theupper surface of the cooling plate 28 is aligned with the lower surfaceof the bonding sheet 32, which is applied onto the plate 22 (refer toFIG. 3( d)). The resulting stacked body is placed in a heat-resistantresin bag, and is then placed in an autoclave. The stacked body in theheat-resistant resin bag is treated for several hours under pressure andheat. Thus, an electrostatic chuck 20 is obtained (refer to FIG. 3( e)).

Next, the third production method will be described with reference tothe explanatory views of FIGS. 4 and 5. First, a frame 70 which is aboard having an opening 70 a having the same shape as a bonding sheet32, and a double-sided adhesive large-size sheet 31 composed of a resinare prepared (refer to FIG. 4( a)). A sheet having a size larger thanthe lower surface of a plate 22 and the upper surface of a cooling plate28 is prepared as the large-size sheet 31. Next, the large-size sheet 31is applied onto the frame 70 so that the large-size sheet 31 covers theopening 70 a of the frame (refer to FIG. 4( b)). Next, the frame 70 towhich the large-size sheet 31 is applied is placed in a dryer, and apre-bake treatment is conducted in an air atmosphere, or in anatmosphere in which air in the dryer is replaced with an inert gas suchas nitrogen or argon, or in an atmosphere in which the pressure in thedryer is reduced to 2,000 Pa or less (preferably 10 Pa or less, and morepreferably 1 Pa or less) (refer to FIG. 4( c)). The pre-bake treatmentis conducted under the same conditions as the first production method.However, the treatment time may be shorter than that in the first andsecond production methods because volatile components are volatilizedfrom both surfaces of the large-size sheet 31. Thus, the amount ofvolatile components in the large-size sheet 31 is reduced. Next, theplate 22 and the cooling plate 28 are prepared (refer to FIG. 5( a)). Aportion of the large-size sheet 31, the portion covering the opening 70a of the frame 70, is sandwiched between the plate 22 and the coolingplate 28 (refer to FIG. 5( b)). The large-size sheet 31 is then cutalong the outer edge of the cooling plate 28. Thus, the large-size sheet31 is formed into a bonding sheet 32 (refer to FIG. 5( c)). Theresulting stacked body is placed in a heat-resistant resin bag, and isthen placed in an autoclave. The stacked body in the heat-resistantresin bag is treated for several hours under pressure and heat. Thus, anelectrostatic chuck 20 is obtained (refer to FIG. 5( d)).

The electrostatic chucks 20 obtained by the first to third productionmethods were heated in a vacuum environment of 100 Pa at 120° C. for 300hours. The amount of change in the weight per square centimeter of thebonding sheet was 25 μg/cm² (where the unit is microgram per squarecentimeter of a bonded surface) or less, and no bubbles were generatedat a bonded interface between the plate 22 and the bonding sheet 32 anda bonded interface between the cooling plate 28 and the bonding sheet32.

Next, a method of producing a showerhead 60 will be described. Theshowerhead 60 can be produced in accordance with any of the first tothird methods of producing an electrostatic chuck 20.

First, a description will be made of a case where a showerhead 60 isproduced in accordance with the first method of producing anelectrostatic chuck 20. First, a ceramic plate 62, a metal electrodeplate 64, and a double-sided adhesive bonding sheet 66 composed of aresin are prepared. The bonding sheet 66 is a sheet similar to thebonding sheet 32. Holes are formed through the plate 62, the metalelectrode plate 64, and the bonding sheet 66 in advance at positionscorresponding to small holes 60 a. Next, the bonding sheet 66 is appliedonto the metal electrode plate 64 so that the holes are aligned witheach other. Next, the metal electrode plate 64 to which the bondingsheet 66 is applied is placed in a dryer, and the above-describedpre-bake treatment is conducted in an air atmosphere, or in anatmosphere in which air in the dryer is replaced with an inert gas suchas nitrogen or argon, or in an atmosphere in which the pressure in thedryer is reduced to 2,000 Pa or less (preferably 10 Pa or less, and morepreferably 0.1 Pa or less). The amount of volatile components in thebonding sheet 66 is reduced by this pre-bake treatment. After thepre-bake treatment, the plate 62 is stacked on the bonding sheet 66,which is applied to the metal electrode plate 64, so that the holes arealigned with each other. The resulting stacked body is placed in aheat-resistant resin bag, and the resin bag is then hermetically sealedby reducing the pressure in the bag. The stacked body and the bagcontaining the stacked body are placed together in an autoclave, and aretreated for 3 to 6 hours at a pressure of 10 to 20 MPa under heating ata temperature 10° C. to 30° C. lower than the temperature of thepre-bake treatment. Thus, the showerhead 60 is obtained.

Next, a description will be made of a case where a showerhead 60 isproduced in accordance with the second method of producing anelectrostatic chuck 20. First, a plate 62, a metal electrode plate 64,and a double-sided adhesive bonding sheet 66 composed of a resin areprepared. The bonding sheet 66 is a sheet similar to the bonding sheet32. Holes are formed through the plate 62, the metal electrode plate 64,and the bonding sheet 66 in advance at positions corresponding to smallholes 60 a. Next, the bonding sheet 66 is applied onto the plate 62 sothat the holes are aligned with each other. Next, the plate 62 to whichthe bonding sheet 66 is applied is placed in a dryer, and theabove-described pre-bake treatment is conducted in an air atmosphere, orin an atmosphere in which air in the dryer is replaced with an inert gassuch as nitrogen or argon, or in an atmosphere in which the pressure inthe dryer is reduced to 2,000 Pa or less (preferably 10 Pa or less, andmore preferably 0.1 Pa or less). The amount of volatile components inthe bonding sheet 66 is reduced by this pre-bake treatment. After thepre-bake treatment, the metal electrode plate 64 is stacked on thebonding sheet 66, which is applied to the plate 62, so that the holesare aligned with each other. The resulting stacked body is placed in aheat-resistant resin bag, and is then placed in an autoclave. Thestacked body in the heat-resistant resin bag is treated for severalhours under pressure and heat. Thus, the showerhead 60 is obtained.

Next, a description will be made of a case where a showerhead 60 isproduced in accordance with the third method of producing anelectrostatic chuck 20. First, a frame which is a board having anopening having the same shape as a bonding sheet 66, and a double-sidedadhesive large-size sheet (sheet having a size larger than the bondingsheet 66) composed of a resin are prepared. Holes are formed through thelarge-size sheet in advance at positions corresponding to small holes 60a. Next, the large-size sheet is applied onto the frame so that thelarge-size sheet covers the opening of the frame. Next, the frame towhich the large-size sheet is applied is placed in a dryer, and theabove-described pre-bake treatment is conducted in an air atmosphere, orin an atmosphere in which air in the dryer is replaced with an inert gassuch as nitrogen or argon, or in an atmosphere in which the pressure inthe dryer is reduced to 2,000 Pa or less (preferably 10 Pa or less, andmore preferably 1 Pa or less). However, the treatment time may beshorter than that in the first and second production methods. Thus, theamount of volatile components in the large-size sheet is reduced. Next,a plate 62 and a metal electrode plate 64 are prepared. A portion of thelarge-size sheet, the portion covering the opening of the frame, issandwiched between the plate 62 and the metal electrode plate 64 so thatthe holes formed in the respective components are aligned with thecorresponding holes. The large-size sheet is then cut along the outeredge of the metal electrode plate 64. Thus, the large-size sheet isformed into a bonding sheet 66. The resulting stacked body is placed ina heat-resistant resin bag, and is then placed in an autoclave. Thestacked body in the heat-resistant resin bag is treated for severalhours under pressure and heat. Thus, the showerhead 60 is obtained.

According to the methods of producing an electrostatic chuck 20 or ashowerhead 60 that have been described in detail above, the contact areabetween the plate 22 and the cooling plate 28 and the contact areabetween the plate 62 and the metal electrode plate 64 do not decrease,and variations in the bonding strength of the contact surface are notgenerated. Specifically, regarding the electrostatic chuck 20, thebonding sheet 32 is heated in advance in a vacuum so as to reduce theamount of volatile components in the bonding sheet 32, and the plate 22and the cooling plate 28 are then bonded by a treatment under pressureand heat. Accordingly, even when the resulting electrostatic chuck 20 isused at high temperatures, gas is not generated from the bonding sheet32, and bubbles are not generated between the plate 22 and the bondingsheet 32 or between the cooling plate 28 and the bonding sheet 32. As aresult, a decrease in the contact area between the plate 22 and thecooling plate 28 does not occur and variations in the bondingperformance are not generated, and thus the temperature uniformity ofthe wafer W subjected to suction is satisfactory. Furthermore, incontrolling the temperature of the wafer W to be constant, the electricpower supplied to the resistance heating element 26 is stabilized, andthus the temperature control can be easily performed. These advantagescan also be similarly achieved in the showerhead 60. Furthermore, in thecase of the electrostatic chuck 20, generated gas does not adhere to thesurface of the plate 22, and thus the responsiveness of applying suctionto and releasing the wafer W can be satisfactorily maintained.

In the first and second methods of producing an electrostatic chuck 20,volatile components are volatilized from one surface of the bondingsheet 32 during the pre-bake treatment. On the other hand, in the thirdproduction method, volatile components are volatilized from bothsurfaces of the large-size sheet 31, and thus the pre-bake treatment canbe completed in a short time. This point also applies to the showerhead60.

It is to be understood that the present invention is not limited to theembodiments described above, and can be implemented in variousembodiments without departing from the technical scope of the presentinvention.

In the above embodiments, an electrostatic chuck 20 including a plate 22having a resistance heating element 26 therein is used. However, thisresistance heating element 26 may be omitted. Also, a showerhead 60including a metal electrode plate 64 having a sheath heater 65 thereinis used in the above embodiments. However, this sheath heater 65 may beomitted.

In the above embodiments, bonding sheets composed of an acrylic resin ora silicone resin are exemplified as the bonding sheets 32 and 66, andconditions of the pre-bake treatment of the bonding sheets have beendescribed in detail. Alternatively, bonding sheets composed of otherresins may be used. In such a case, conditions of the pre-bake treatment(such as the treatment temperature and the treatment time) suitable forthe resins are determined in advance by experiments. Specifically, asdescribed in Examples below, a relationship among the treatmenttemperature, the treatment time, and the appearance of a bondedinterface (e.g., the occurrence or non-occurrence of separation) isexamined in advance, and the conditions are then determined.

EXAMPLES Reference Example

Gas components generated from a bonding sheet composed of an acrylicresin were analyzed by dynamic headspace-gas chromatography-massspectrometry (DHS-GC-MS). Specifically, a bonding sheet composed of anacrylic resin was placed in a chamber, and the chamber was evacuated toa high vacuum state. Subsequently, the chamber was heated to apredetermined temperature (60° C., 80° C., 100° C., or 120° C.), and acarrier gas was supplied in this state at a flow rate of 500 mL/min. Agenerated gas was collected on an adsorbent and concentrated, and gascomponents were then analyzed by gas chromatography-mass spectrometry(GC-MS). Electron impact (EI; 70 eV) was employed as an ionizationmethod of the mass spectrometer. FIG. 8 includes charts showing theanalytical results. FIG. 8 shows that the gas components generated fromthis bonding sheet are mainly hydrocarbon compounds.

Example 1

An electrostatic chuck in which an alumina plate 22 having a diameter φof 297 mm and a thickness of 3 mm is bonded to an aluminum (Al) coolingplate 28 having a diameter φ of 297 mm and a thickness of 18 mm with anacrylic resin bonding sheet 32 having a thickness of 0.15 mm wasproduced as an example of an electrostatic chuck 20. This electrostaticchuck 20 was produced in accordance with the first production methoddescribed above. Specifically, a bonding sheet 66 was applied onto theAl cooling plate 28, and a pre-bake treatment was then conducted. In thepre-bake treatment, the temperature was increased at a rate of 32° C./hin a special furnace in which the pressure was reduced to 10 Pa or less.When the temperature reached 120° C., the temperature was controlled tobe constant and maintained at 120° C. for 20 hours. The temperature wasthen decreased at a rate of 4° C./h. The cooling plate 28 to which thebonding sheet 66 was applied was then bonded to the plate 22.Specifically, the cooling plate 28 and the plate 22 were aligned withand temporarily bonded to each other, and the resulting temporarilybonded body was then placed in a heat-resistant resin bag. The resin bagwas degassed until the pressure in the bag was reduced to 1,000 Pa orless, and was then sealed. Next, the temporarily bonded body and the bagcontaining the temporarily bonded body were subjected to a bondingtogether in an autoclave by a treatment under pressure and heat. Thebonding treatment under pressure and heat was conducted under theconditions of 100° C. and a pressure of 14 MPa for four hours.

Comparative Example 1

The electrostatic chuck 20 of Example 1 was produced by an existingmethod. Specifically, the electrostatic chuck 20 was produced by thesame method as in Example 1 except that the pre-bake treatment inExample 1 was not performed.

Confirmation of Effect of Example 1 and Comparative Example 1

The electrostatic chucks 20 of Example 1 and Comparative Example 1 wereeach placed in a chamber 12 as shown in FIG. 1, and a test forconfirming the effect was conducted. A certain amount of cooling waterat 45° C. was made to flow in a cooling medium path 30 of the coolingplate 28 of the electrostatic chuck 20, and an electric power wassupplied to a resistance heating element 26 buried in the plate 22.Thus, the electric power supplied to the resistance heating element 26was controlled so that the surface temperature of the plate 22 became apredetermined temperature (90° C. in Example 1 and 80° C. in ComparativeExample 1). The surface temperature of the plate 22 was measured bybringing a thermocouple into contact with the center of the plate 22.According to the results, after 100 hours from the start of control, theelectric power was decreased by close to 20% in Comparative Example 1,whereas the electric power was decreased by only about 1% in Example 1,though the predetermined temperature was higher. FIG. 9 shows theresults of this test. This change in the electric power means thatbubbles are generated at the bonded interface, and heat transfer betweenthe plate 22 and the cooling plate 28 changes so as to become small.Specifically, in the case where a certain electric power is supplied inthe chamber, the surface temperature of the plate 22 changes so as toincrease in a portion of the bonded interface where the bubbles aregenerated. Furthermore, the bubbles are unevenly generated in the plane,and the surface temperature distribution of the plate 22 changes. Whenthe temperature or the temperature distribution of the surface of theplate 22 changes, the reactive species in the plasma significantlychanges. Consequently, for example, the etching rate in an etching stepvaries in the plane of a wafer, resulting in a decrease in the yield ofdevices.

In order to confirm the above phenomenon, the electric power supplied tothe resistance heating element 26 was controlled so that the surfacetemperature of each of the electrostatic chucks 20 of Example 1 andComparative Example 1 became 65° C., and the temperature distribution ofthe surface of each of the electrostatic chucks 20 was measured. InExample 1, the highest temperature was 66.2° C., the lowest temperaturewas 62.5° C., the average temperature was 64.6° C., and the temperaturerange (=the highest temperature−the lowest temperature) was 3.7° C. InComparative Example 1, the highest temperature was 66.3° C., the lowesttemperature was 62.7° C., the average temperature was 64.8° C., and thetemperature range (=the highest temperature−the lowest temperature) was3.6° C. There was no difference between Example 1 and ComparativeExample 1. Subsequently, the surface temperature distribution of theplate 22 after 300 hours from the start of control was examined. InExample 1, the highest temperature was 66.4° C., the lowest temperaturewas 62.5° C., the average temperature was 64.8° C., and the temperaturerange (=the highest temperature−the lowest temperature) was 3.9° C. Incontrast, in Comparative Example 1, the highest temperature was 67.7°C., the lowest temperature was 62.3° C., the average temperature was65.1° C., and the temperature range was 5.4° C. These results show thatthe temperature uniformity of the plate 22 in Example 1 was stable ascompared with Comparative Example 1.

Example 2

A showerhead including a silicon carbide (SiC) plate 62 having adiameter φ of 430 mm and a thickness of 4 mm and a metal electrode plate64 composed of aluminum (Al), having a tapered outer circumference witha diameter φ of one surface of 430 mm and a diameter φ of anothersurface of 450 mm, and having a thickness of 20 mm, the plate 62 and themetal electrode plate 64 being bonded to each other with a siliconeresin bonding sheet 66 having a thickness of 0.25 mm therebetween, wasproduced as an example of a showerhead 60. Small holes 60 a each had adiameter φ of 0.1 mm, and the distance between adjacent small holes 60 awas 4 mm. This showerhead 60 was produced in accordance with the secondproducion method described above. Specifically, the bonding sheet 66 wasapplied onto the SiC plate 62, and a pre-bake treatment was thenconducted. In the pre-bake treatment, the temperature of the plate 62was increased at a rate of 10° C./h in a special furnace in which thepressure was reduced to 10 Pa or less. When the temperature reached 150°C., the temperature was controlled to be constant and maintained at 150°C. for 20 hours. The temperature was then decreased at a rate of 5°C./h. The plate 62 to which the bonding sheet 66 was applied was thenbonded to the metal electrode plate 64. Specifically, the plate 62 andthe metal electrode plate 64 were aligned with and temporarily bonded toeach other, and the resulting temporarily bonded body was then placed ina heat-resistant resin bag. The resin bag was degassed until thepressure in the bag was reduced to 1,000 Pa or less, and was thensealed. Next, the temporarily bonded body and the bag containing thetemporarily bonded body were subjected to a bonding together in anautoclave by a treatment under pressure and heat. The bonding treatmentunder pressure and heat was conducted under the conditions of 100° C.and a pressure of 14 atm for five hours.

Comparative Example 2

The showerhead 60 of Example 2 was produced by an existing method.Specifically, the showerhead 60 was produced by the same method as inExample 2 except that the pre-bake treatment in Example 2 was notperformed.

Confirmation of Effect of Example 2 and Comparative Example 2

The showerheads 60 of Example 2 and Comparative Example 2 were eachplaced in a chamber 12 shown in FIG. 1, and a test for confirming theeffect was conducted. The showerhead 60 was arranged and fixed so thatthe upper surface of the metal electrode plate 64 contacted a coolingplate 68 attached to the chamber 12. Next, a certain amount of coolingwater at 60° C. was made to flow in a cooling medium path 72 of thecooling plate 68, and an electric power was supplied to a sheath heater65 buried in the metal electrode plate 64. Thus, the electric powersupplied to the sheath heater 65 was controlled so that the surfacetemperature of the plate of the showerhead 60 became 90° C. The surfacetemperature of the plate was measured by a thermocouple fixed to thesurface of the plate with a ceramic bond, and was used for thetemperature control. According to the results, after 70 hours from thestart of control, the electric power was decreased by 8% in ComparativeExample 2, whereas the electric power was decreased by only about 3% inExample 2. FIG. 10 shows the results of this test. This change in theelectric power shows that the temperature of the surface of the plate 62of the showerhead 60 significantly changes. Specifically, when the heatinput from the plasma and the temperature of the surface of the plate 62change, the reactive species in the plasma significantly changes.Consequently, for example, the etching rate in an etching step varies inthe plane of a wafer, resulting in a decrease in the yield of devices.In fact, the yield (percentage of the number of acceptable products tothe total number of products) in the etching step in Comparative Example2 was 88%, whereas the yield was 99% or more in Example 2.

Examination of Pre-Bake Conditions of Acrylic Resin Sheet

A surface of a double-sided adhesive bonding sheet composed of anacrylic resin was applied onto a transparent glass plate, which was adummy of a plate of an electrostatic chuck. The transparent glass platewas placed in a vacuum dryer in a state in which the other surface ofthe bonding sheet was exposed, and the pressure in the dryer was reducedto 10 Pa or less (7 to 8 Pa). A pre-bake treatment was then conducted.Specifically, heating was conducted under the conditions of eachtreatment temperature and each treatment time shown in Table 1 belowwhile maintaining this pressure. After the pre-bake treatment, anothertransparent glass plate, which was a dummy of a cooling plate, wasplaced on the bonding sheet applied to the transparent glass plate, andtemporarily bonded to the bonding sheet. The resulting temporarilybonded body was then placed in a heat-resistant resin bag. The air inthe heat-resistant resin bag was evacuated until the pressure in the bagreduced to 1,000 Pa or less, and the bag was then hermetically sealed.The bag was then placed in an autoclave furnace, and heated at 100° C.at 14 atm for five hours to obtain a glass-glass bonded body in whichthe pair of transparent glass plates are bonded to each other with thebonding sheet therebetween. Here, the bonding performance at the bondedinterface between each glass plate and the bonding sheet was observed.The results are shown in Table 1. As shown in Table 1, when thetemperature in the pre-bake treatment was in the range of 110° C. to130° C., the bonding was satisfactorily performed. However, at 140° C.,separation or the like occurred, and the bonding performance was notsatisfactory.

TABLE 1 Treatment Treatment Time Temperatue 10 hrs 15 hrs 20 hrs 30 hrs40 hrs 110° C. Satisfactory Satisfactory Satisfactory SatisfactorySatisfactory 120° C. Satisfactory Satisfactory Satisfactory SatisfactorySatisfactory 130° C. Satisfactory Satisfactory Satisfactory SatisfactorySatisfactory 140° C. Unsatisfactory Unsatisfactory UnsatisfactoryUnsatisfactory Unsatisfactory

Next, the glass-glass bonded body obtained as described above was heatedat 120° C. at 100 Pa for 300 hours, and the presence or absence ofdefects (presence or absence of bubbles) at the bonded interface betweeneach glass plate and the bonding sheet was examined (evaluation test).The results are shown in Table 2 below. Furthermore, an Al plate-Alplate bonded body was prepared by using Al plates instead of thetransparent glass plates in accordance with the above method ofproducing the glass-glass bonded body, and a change in the thermalconductivity was examined. The results are shown in Table 3 below. Thethermal conductivity was measured by the heat flow meter method (inaccordance with JIS-A1412, ASTM-0518, and ISO8301). Each of thenumerical values (%) shown in Table 3 is a change ratio of the valuemeasured after the above-described evaluation test to a reference valuemeasured immediately after producing the Al plate-Al plate bonded body.Referring to the results shown in Tables 2 and 3, in the case where theacrylic resin bonding sheet is used, the treatment temperatures and thetreatment times shown by symbol ◯ in Table 4 are suitable for thepre-bake conditions. Pre-bake conditions of a treatment temperature of110° C. to 130° C. and a treatment time of 40 hours also providedsatisfactory results. However, these pre-bake conditions are notpreferable because the treatment time is unnecessarily long, therebydecreasing productivity.

TABLE 2 Treatment Treatment Time Temperature 10 hrs 15 hrs 20 hrs 30 hrs40 hrs 110° C. Bubbles Bubbles Bubbles Bubbles No defect present presentpresent present 120° C. Bubbles No defect No defect No defect No defectpresent 130° C. Bubbles No defect No defect No defect No defect present

TABLE 3 Treatment TreatmentTime Temperature 10 hrs 15 hrs 20 hrs 30 hrs40 hrs 110° C. 8% 8% 8% 7% 3% 120° C. 8% 3% 3% 3% 2% 130° C. 7% 2% 2% 2%2%

TABLE 4 Treatment Treatment Time Temperature 10 hrs 15 hrs 20 hrs 30 hrs40 hrs 110° C. ◯ 120° C. ◯ ◯ ◯ ◯ 130° C. ◯ ◯ ◯ ◯ 140° C.

Examination of Pre-Bake Conditions of Silicone Resin Sheet

A surface of a double-sided adhesive bonding sheet composed of asilicone resin was applied onto a transparent glass plate, which was adummy of a plate of an electrostatic chuck. The transparent glass platewas placed in a vacuum dryer in a state in which the other surface ofthe bonding sheet was exposed, and the pressure in the dryer was reducedto 10 Pa or less (7 to 8 Pa). A pre-bake treatment was then conducted.Specifically, heating was conducted under the conditions of eachtreatment temperature and each treatment time shown in Table 5 belowwhile maintaining this pressure. After the pre-bake treatment, anothertransparent glass plate, which was a dummy of a cooling plate, wasplaced on the bonding sheet applied to the transparent glass plate, andtemporarily bonded to the bonding sheet. The resulting temporarilybonded body was then placed in a heat-resistant resin bag. The air inthe heat-resistant resin bag was evacuated, and the bag was thenhermetically sealed. The bag was then placed in an autoclave furnace,and heated at 100° C. at 14 atm for five hours to obtain a glass-glassbonded body in which the pair of transparent glass plates are bonded toeach other with the bonding sheet therebetween. Here, the bondingperformance at the bonded interface between each glass plate and thebonding sheet was observed. The results are shown in Table 5. As shownin Table 5, when the temperature in the pre-bake treatment was in therange of 120° C. to 170° C., the bonding was satisfactorily performed.However, at 180° C., separation or the like occurred, and the bondingperformance was not satisfactory.

TABLE 5 Treatment Treatment Time Temperature 10 hrs 15 hrs 20 hrs 30 hrs40 hrs 120° C. Satisfactory Satisfactory Satisfactory SatisfactorySatisfactory 140° C. Satisfactory Satisfactory Satisfactory SatisfactorySatisfactory 160° C. Satisfactory Satisfactory Satisfactory SatisfactorySatisfactory 170° C. Satisfactory Satisfactory Satisfactory SatisfactorySatisfactory 180° C. Unsatisfactay Unsatisfactory UnsatisfactoryUnsatisfactory Unsatisfactory

Next, the glass-glass bonded body obtained as described above was heatedat 120° C. at 100 Pa for 300 hours, and the presence or absence ofdefects (presence or absence of bubbles) at the bonded interface betweeneach glass plate and the bonding sheet was examined (evaluation test).The results are shown in Table 6 below. Furthermore, an Al plate-Alplate bonded body was prepared by using Al plates instead of thetransparent glass plates in accordance with the above method ofproducing the glass-glass bonded body, and a change in the thermalconductivity was examined. The results are shown in Table 7 below. Themethod for measuring the thermal conductivity and the numerical values(%) shown in Table 7 are the same as those described above. Referring tothe results shown in Tables 6 and 7, in the case where the siliconeresin bonding sheet is used, the treatment temperatures and thetreatment times shown by symbol ◯ in Table 8 are suitable for thepre-bake conditions. Pre-bake conditions of a treatment temperature of140° C. to 170° C. and a treatment time of 40 hours also providedsatisfactory results. However, these pre-bake conditions are notpreferable because the treatment time is unnecessarily long, therebydecreasing productivity.

TABLE 6 Treatment Treatment Time Temperature 10 hrs 15 hrs 20 hrs 30 hrs40 hrs 120° C. Bubbles Bubbles Bubbles Bubbles Bubbles present presentpresent present present 140° C. Bubbles No defec tNo defect No defect Nodefect present 160° C. Bubbles No defect No defect No defect No defectpresent 170° C. Bubbles No defect No defect No defect No defect present

TABLE 7 Treatment Treatment Time Temperature 10 hrs 15 hrs 20 hrs 30 hrs40 hrs 120° C. 8% 8% 8% 8% 8% 140° C. 8% 3% 3% 3% 2% 160° C. 8% 2% 2% 2%2% 170° C. 8% 2% 2% 1% 1%

TABLE 8 Treatment Treatment Time Temperature 10 hrs 15 hrs 20 hrs 30 hrs40 hrs 120° C. 140° C. ◯ ◯ ◯ ◯ 160° C. ◯ ◯ ◯ ◯ 170° C. ◯ ◯ ◯ ◯ 180° C.

Next, a glass-glass bonded body was produced by the same method as themethod described above except that, in producing a glass-glass bondedbody using a bonding sheet composed of a silicone resin, the pressure inthe dryer during the pre-bake treatment was set to 0.01 Pa, and heatingwas conducted under the conditions of each treatment temperature andeach treatment time shown in Table 9 below while maintaining thispressure. This glass-glass bonded body was heated at 160° C. at 100 Pafor 300 hours, and the presence or absence of defects (presence orabsence of bubbles) at the bonded interface between each glass plate andthe bonding sheet was examined (evaluation test). The results are shownin Table 9. As is apparent from Table 9, in the glass-glass bonded bodysubjected to the pre-bake treatment under the conditions of a highvacuum of 0.01 Pa and the appropriate treatment temperature andtreatment time shown in Table 8, no bubbles were generated at the bondedinterface even at a high temperature of 160° C. in the evaluation test.

TABLE 9 Treatment Treatment Time Temperature 10 hrs 15 hrs 20 hrs 30 hrs40 hrs 120° C. Bubbles Bubbles Bubbles Bubbles Bubbles present presentpresent present present 140° C. Bubbles No defect No defect No defect Nodefect present 160° C. Bubbles No defect No defect No defect No defectpresent 170° C. Bubbles No defect No defect No defect No defect present

Examination of Atmosphere of Pre-Bake Treatment of Silicone Resin Sheet

In the above Examination of pre-bake conditions of silicone resin sheet,the atmosphere of the dryer during the pre-bake treatment was changed toair, and heat treatment was conducted under an ambient pressure of 1 atmat 170° C. for 30 hours. A glass bonded body and an Al bonded body wereprepared under the same conditions as the above Examination of pre-bakeconditions of silicone resin sheet except for the above, and wereevaluated by the evaluation test described above. According to theresults, there were no bubbles at the bonded interface of the glassbonded body, and a change in the thermal conductivity of the Al bondedbody was 3%.

Furthermore, in the above Examination of pre-bake conditions of siliconeresin sheet, the atmosphere of the dryer during the pre-bake treatmentwas changed to nitrogen gas, and heat treatment was conducted under anitrogen atmosphere of 1 atm at 170° C. for 15 hours. A glass bondedbody and an Al bonded body were prepared under the same conditions asthe above Examination of pre-bake conditions of silicone resin sheetexcept for the above, and were evaluated by the evaluation testdescribed above. According to the results, there were no bubbles at thebonded interface of the glass bonded body, and a change in the thermalconductivity of the Al bonded body was 3%. Note that, also in the casewhere argon was used instead of nitrogen, the same results as in thecase of nitrogen were obtained.

According to the above results, the atmosphere of the pre-bake treatmentmay be air, nitrogen, or argon at 1 atm, and the pre-bake treatment ismore preferably conducted in a vacuum in order to further decrease thechange in the thermal conductivity.

INDUSTRIAL APPLICABILITY

The present invention is applicable as, for example, an electrostaticchuck.

What is claimed:
 1. A ceramic-metal bonded body comprising a ceramicplate, a metal supporting base, and a resin bonding sheet that bonds theplate to the supporting base, wherein when the bonded body is heated ina vacuum environment of 100 Pa at 120° C. for 300 hours, the amount ofchange in the weight of the bonding sheet is 50 μg/cm², where the unitis microgram per square centimeter of a bonded surface, or less.
 2. Aceramic-metal bonded body comprising a ceramic plate, a metal supportingbase, and a resin bonding sheet that bonds the plate to the supportingbase, wherein when the bonded body is heated in a vacuum environment of100 Pa at 120° C. for 300 hours, no bubbles are generated at a bondedinterface between the plate and the bonding sheet and a bonded interfacebetween the supporting base and the bonding sheet.
 3. The ceramic-metalbonded body according to claim 1, wherein the ceramic-metal bonded bodyis an electrostatic chuck used for fixing a wafer by applying suction ina semiconductor manufacturing process or a showerhead used for supplyingand dispersing a reactant gas to a chamber in a semiconductormanufacturing process.
 4. The ceramic-metal bonded body according toclaim 2, wherein the ceramic-metal bonded body is an electrostatic chuckused for fixing a wafer by applying suction in a semiconductormanufacturing process or a showerhead used for supplying and dispersinga reactant gas to a chamber in a semiconductor manufacturing process.